NPRM on CL300 Trim Actuator

An FAANPRM for the Challenger 300horizontal stabilizer trim actuator states the No Back and the Number 1 motor brake assembly can both fail dormant. “…failure of the [system] along with additional component failure could result in an uncontrollable horizontal stabilizer surface runaway without the ability to retrim [and] could lead to the loss of the airplane.” A proposed new Airworthiness Limitation Task consists of a functional test to ensure that a dormant failure is detected and corrected. The FAA is accepting comments until November 25.